Just a little question re mixtures of IPA and water. Let's say you want
a 75% mixture. Do you...
a) weigh 75 g of IPA and 25 g of H2O? If so, at what temperature for
each component?
b) measure 75 ml of IPA and add 25 ml of water? If so, at what
temperature for each component?
c) measure 75 ml of IPA and add water to make up to 100 ml? If so, at
what temperature for each component?
d) measure 25 ml of water and add IPA to make up to 100 ml? If so, at
what temperature for each component?
Assuming the temperature is the same for the two components (big if, in
many cases!), each of the four solutions above will be very different
from each other (of course, also applies to 50% solutions). The problem
is because mixtures of the two liquids do not form an ideal solution.
The loose structure of the water molecules leaves space for the tight
structure of the IPA molecules to fit in (simplified explanation - look
up wiki Ideal Solution.)
If you do a scientific test with each of the four mixtures, you will
find that the measured conductivity after injecting a known quantity of
a test solution will vary by up to 15%.
Just a thought...
Brian Ellis
On 29/06/2017 00:25, Joe Russeau wrote:
> Hello Rich,
>
> To the best of my knowledge, I am not aware of a statement to that
> affect in any IPC document that I have read. If there is such a
> statement, then I would say it is an erroneous one and needs to be
> addressed. There is HPLC grade IPA, which usually refers to 99.5% or
> higher purity. There is also Electronic-grade IPA, which has the same
> purity as HPLC. Then there is Technical grade IPA, which I believe is
> usually classified as anything above 90% purity. IPA is a chemical and
> its percentage of purity doesn't define whether or not it is still an
> "IPA", it's chemical formula defines that. The % only defines how much
> junk is left behind in the solvent. Now, there are IPC methods that
> deal with the percentage of the starting IPA, such as the ROSE and Ion
> Chromatography methods, and the reason is to minimize adding error into
> the measurement system that could skew the results for an actual
> sample. If there is a statement as you indicate below, can you ask
> whoever told you that which IPC document states such a thing? If not, I
> wonder if someone might have misread that part of the document
>
> Best Regards,
>
> Joe Russeau
>
>
>
> -----Original Message----- From: Richard Kraszewski
> Sent: Wednesday, June 28, 2017 4:48 PM
> To: [log in to unmask]
> Subject: [TN] IPC definition of alcohol
>
> I have been lead to believe that there is a definition within IPC
> documentation for IPA (isopropyl alcohol).
> That it defines that anything greater than "XX%" IPA shall be
> considered IPA.
>
> Any thoughts?
>
>
> Rich Kraszewski
> Senior Staff Process Engineer
> Plexus Engineering Solutions
> Ship To - 2444 Schultz Dr. Neenah, WI 54957-2444
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> www.plexus.com/(NASDAQ PLXS)
> [log in to unmask]
>
>
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